1. The writing is OK. It's not entirely clear, however, how you expect the money. If you want $10 in quarters, three $20 bills and five $5 bills, you need to specify.
2. In AmE we call a person working behind the counter in a bank a "teller."
3. "Bills" or simply "paper money" would be common. Like I used "$20 bills" above.
Student or Learner